The slow spreading Reykjanes Ridge overlies the Iceland hotspot and has undergone well ordered changes in crustal segmentation. Previous studies have attributed these changes to varying mantle plume thermal effects, rendering the lithosphere ductile or brittle. Here we use seafloor spreading magnetic anomalies to show that crustal accretion has been focused throughout its spreading history and to determine the detailed evolution of Reykjanes Ridge segments. By ∼53 Ma, organized spreading had developed on an orthogonally spreading linear axis following continental breakup. After a plate motion change at ∼38 Ma, orthogonally spreading offset ridge segments formed by ridge propagation forming varying length fracture zones. From then to the present, the offset segments diachronously migrated back to the original linear geometry from north to south replacing orthogonal with oblique spreading as the axis became linear again. Fracture zones were not terminated, however, simply by reducing segment offsets even to zero. Their termination involved the axial propagation of buoyant upwelling instabilities across the discontinuities, correspondingly extending V-shaped crustal ridges southward. This evolution was guided by a persistent linear deep damp mantle melting interval maintained by the episodic propagation of buoyant upwelling instabilities. Our study indicates that at slow spreading ridges, where buoyant upwelling instabilities govern crustal segmentation, spatial gradients in mantle melting properties may direct the behavior of the instabilities. Where ridges overlie regional hotspot gradients in mantle melting, buoyant instabilities may propagate systematically, and plate boundary evolution may follow an organized pattern.

中文翻译：

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雷克雅内斯山脊的运动学：冰岛热点对板块边界演化的影响

缓慢扩张的雷克雅内斯海岭覆盖在冰岛热点之上，并经历了地壳分割的有序变化。先前的研究将这些变化归因于不同的地幔羽流热效应，使岩石圈具有延性或脆性。在这里，我们使用海底扩张磁异常来表明地壳吸积在其扩张历史中一直受到关注，并确定雷克雅内斯海岭部分的详细演化。到大约 53 Ma，大陆分裂后，有组织的扩张已经在正交扩张的线性轴上发展起来。在约 38 Ma 的板块运动变化之后，通过脊传播形成正交扩展的偏移脊段，形成不同长度的断裂带。从那时到现在，随着轴线再次变为线性，偏移线段从北到南历时地迁移回原来的线性几何形状，用倾斜扩展取代正交。然而，仅仅通过将段偏移减少到零，断裂区并没有被终止。它们的终止涉及浮力上升流不稳定性在不连续性上的轴向传播，相应地向南延伸了 V 形地壳脊。这种演化是由浮力上涌不稳定性的间歇性传播维持的持续线性深部潮湿地幔熔化区间引导的。我们的研究表明，在缓慢扩张的海脊处，浮力上升流不稳定性控制地壳分段，地幔熔化特性的空间梯度可能指导不稳定性的行为。在洋脊覆盖地幔熔融区域热点梯度的地方，浮力不稳定性可能会系统地传播，板块边界演化可能遵循有组织的模式。